Magnetic storage systems typically include a rotatable magnetic disk having concentric data tracks defined for storing data, and a magnetic recording head or transducer for reading data from and writing data to the various data tracks. In typical disk drive systems, a stack of one or more magnetic disks is mounted over a spindle on a drive motor. The system also includes a head actuator for moving the magnetic recording head relative to the disk surfaces, and electronic circuitry for processing signals to implement various functions of the disk drive.
The head is attached to a carrier or slider having an air bearing surface which is supported during operation adjacent to the data surface of the disk by a cushion of air generated by the rotating disk. The terms “head” and “slider” are sometimes both used to refer to the slider having a head attached thereon. The slider design affects the efficiency, density, speed and accuracy with which the data can be read and written to the disk. Recording density generally depends on the separation distance (also known as the flying height) between the recording element of the head and the disk. Lower flying heights are usually desired to achieve high areal density recording. As flying height is reduced, it becomes increasingly difficult to maintain the flying height accuracy to the degree necessary for reliable reading and recording of data. In addition, lower flying heights can lead to undesirable interactions between the head and the disk.
The slider is typically fabricated from a hard ceramic material, and the disk typically includes a hard carbon coating. The slider material is chosen so that any interactions between the disk and air bearing surface of the slider will not result in premature wear or breakage of the slider. In addition, the slider material should be relatively inert so that no chemical reactions take place on the air bearing surface. As illustrated in FIG. 1, sliders are usually derived from a wafer 10 made from a ceramic material such as a mixture of aluminun oxide (Al2O3) and titanium carbide (TiC). The components of each read/write device are formed or deposited on a surface 12 of the wafer 10 and the wafer 10 is diced into rows such as row 20 illustrated in FIG. 2. The row 20 has an end surface 12 having the read/write device and a row face that is processed, usually by polishing and/or etching, to form an air bearing surface 18. The row 20 is then diced into individual sliders 30 having an air bearing surface 18 and a read/write device surface 12 on which the read/write device is typically located at a central position 32, as illustrated in FIG. 3. The end surface 12 of the slider at the position where the read/write device is located may also be known as the trailing edge. FIG. 4a illustrates a slider 30 having a leading edge 14, a trailing edge 12, an air bearing side 18, a back or flex side 22, and x and y directions. FIG. 4b illustrates a side view of the slider 30 from the y direction and shows a disk 40 over which the slider 30 flies.
The slider is often formed with an aerodynamic pattern of protrusions (air bearing pattern) on the air bearing surface which enable the slider to fly at a constant height close to the disk during operation of the disk drive. It has been found that several important characteristics of the slider related to obtaining the desired flying characteristics for the slider are crown, camber and twist. These characteristics relate to the curvature of the slider. Crown is the deviation from an imaginary planar surface in the direction of air flow (x-direction, or leading edge to trailing edge), with a concave air bearing surface shape defined as negative crown and a convex shape defined as positive crown. Similarly, camber is the deviation from the same imaginary planar surface in the y-direction (normal to the direction of air flow). A concave air bearing surface shape is defined as negative camber and a convex shape is defined as positive camber. Twist is the difference between the diagonal curvatures. The crown is the maximum spacing between the surface of back side 22 and the dotted line in FIG. 4b, which is along the x-direction. Similarly, the camber is the maximum spacing between the back surface and a dotted line along the y-direction, and the twist is the difference in diagonal curvatures. For typical slider designs, neither negative crown nor negative camber of the air bearing surface is desired because it leads to variations in the slider flying height and also makes it more likely that the edges and corners of the slider will damage the recording medium should there be contact between them. It should be understood that in the difference calculation for twist, a positive or a negative twist value is possible. The mathematical sign for the twist value therefore depends on the choice of the order of the two diagonal curvatures in the subtraction. Thus, a positive twist can be interpreted as a negative twist of the same magnitude if the order of the two diagonal curvatures in calculating their difference is reversed. An interpretation of the sign convention for twist, opposite to that described in this invention, should not limit the scope of embodiments of the present invention.
Adjusting any one parameter of the crown, camber and twist may lead to changes in the other parameters, as they all pertain to the same surface. It has been difficult to control these parameters because when an operation is carried out to control one parameter, the others may change in an unpredictable and undesirable manner.